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We live in a gigantic star city. Our Milky Way galaxy contains an estimated 200 billion stars. But that's just the bare tip of the iceberg. The Milky Way is surrounded by vast amounts of an unknown material called dark matter that is invisible because it doesn't release any radiation. Astronomers know it exists because, dynamically, the galaxy would fly apart if dark matter didn't keep a gravitational lid on things.

Still, astronomers would like to have a precise measure of the galaxy's mass to better understand how the myriad galaxies throughout the universe form and evolve. Other galaxies can range in mass from around a billion solar masses to 30 trillion solar masses. How does our Milky Way compare?

Curious astronomers teamed up the Hubble Space Telescope and European Space Agency's Gaia satellite to precisely study the motions of globular star clusters that orbit our galaxy like bees around a hive. The faster the clusters move under the entire galaxy's gravitational pull, the more massive it is. The researchers concluded the galaxy weighs 1.5 trillion solar masses, most of it locked up in dark matter. Therefore, the Milky Way is a "Goldilocks" galaxy, not too big and not too small. Just right!

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    • By NASA
      “Trying to do stellar observations from Earth is like trying to do birdwatching from the bottom of a lake.” James B. Odom, Hubble Program Manager 1983-1990.

      The third servicing mission to the Hubble Space Telescope, placed in orbit in 1990, occurred during the STS-103 mission in December 1999. During the mission, originally planned for June 2000 but accelerated by six months following unexpected failures of the telescope’s attitude control gyroscopes, the astronauts restored the facility to full functionality. During their eight-day mission that featured the first space shuttle crew to spend Christmas in space, the seven-member U.S. and European crew rendezvoused with and captured Hubble, and four astronauts in rotating teams of two conducted three lengthy and complex spacewalks to service and upgrade the telescope. They redeployed the telescope with greater capabilities than ever before to continue its mission to help scientists unlock the secrets of the universe.
      Schematic showing the Hubble Space Telescope’s major components. Workers inspect the Hubble Space Telescope’s 94-inch diameter primary mirror prior to assembly. Astronauts release the Hubble Space Telescope in April 1990 during the STS-31 mission. The discovery after the Hubble Space Telescope’s launch in 1990 that its primary mirror suffered from a flaw called spherical aberration disappointed scientists who could not obtain the sharp images they had expected. But thanks to the Hubble’s built-in feature of on-orbit servicing, NASA devised a plan to correct the telescope’s optics during the first planned repair mission in 1993. A second servicing mission in 1997 upgraded the telescope’s capabilities until the next mission planned for three years later. But after three of the telescope’s six gyroscopes failed in 1997, 1998, and 1999, mission rules dictated a call up mission in case additional gyroscope failures sent Hubble into a safe mode. NASA elected to move up some of the servicing tasks from the third mission, splitting it into missions 3A and 3B, planning to fly 3A in October 1999 on Discovery’s STS-103 mission primarily to replace the failed gyroscopes. Delays to the shuttle fleet resulting from anomalies during the launch of STS-93 in July 1993 slipped STS-103 first into November and ultimately into December. Technical issues with Discovery itself pushed the launch date to mid-December, and raised concerns about having a shuttle in orbit during the Y2K transition. Once the launch had slipped to Dec. 19, mission planners cut the mission from 10 to eight days, deleting one of the four spacewalks, to ensure a return before the end of the calendar year. The servicing mission couldn’t come soon enough, as a fourth gyroscope failed aboard Hubble in mid-November, with Discovery already poised on the launch pad to prepare for STS-103. Controllers placed Hubble in a safe mode until the astronauts arrived.
      The STS-103 crew of C. Michael Foale, left, Claude Nicollier, Scott J. Kelly, Curtis L. Brown, Jean-François A. Clervoy, John M. Grunsfeld, and Steven L. Smith. The STS-103 crew patch. The mission patch for the Hubble Servicing Mission-3A. To execute the third Hubble Servicing Mission, in July 1998 NASA selected an experienced four-person team to carry out a record-breaking six spacewalks on the flight then planned for June 2000. The spacewalkers included Mission Specialists Steven L. Smith serving as payload commander, John M. Grunsfeld, C. Michael Foale, and European Space Agency (ESA) astronaut Claude Nicollier from Switzerland. The addition in March 1999 of Commander Curtis L. Brown, Pilot Scott J. Kelly, and Mission Specialist ESA astronaut Jean-François A. Clervoy of France rounded out the highly experienced crew with 18 previous spaceflights among them. Brown earned the distinction as only the fifth person to fly in space six times. For Kelly, STS-103 marked his first spaceflight. Smith, Clervoy, and Grunsfeld each had flown two previous missions, Foale four including a long-duration mission aboard Mir, and Nicollier three. Smith participated in three spacewalks during the second Hubble Servicing Mission and Nicollier served as the Remote Manipulator System (RMS) or robotic arm operator during the first.
      The STS-103 crew at the traditional prelaunch breakfast at NASA’s Kennedy Space Center in Florida. Suited up, the STS-103 astronauts leave crew quarters for the trip to Launch Pad 39B. Space shuttle Discovery on Launch Pad 39B, awaiting launch. Discovery arrived back to KSC at the end of the STS-96 mission on June 6, 1999, and workers towed it to the Orbiter Processing Facility the same day to begin readying it for STS-103. The vehicle rolled over to the Vehicle Assembly Building on Nov. 4, where workers mated it with its external tank and twin solid rocket boosters, before rolling the stack out to Launch Pad 39B on Nov. 13.
      Liftoff of space shuttle Discovery on the STS-103 Hubble Space Telescope servicing mission 3A. The Hubble Space Telescope as Discovery approaches. The STS-103 crew berthing the Hubble into the payload bay. Beginning its 27th trip into space, Discovery lifted off from Launch Pad 39B at 7:50 p.m. EST on Dec. 19 to fix the ailing space telescope. Two days later, Brown and Kelly maneuvered Discovery to within range of Hubble so Clervoy operating the 50-foot-long RMS could grapple the telescope and berth it into the payload bay.
      During the first spacewalk, astronauts John M. Grunsfeld, left, and Steven L. Smith replacing one of the Rate Sensor Units containing two gyroscopes. Smith gives a thumbs up with his image reflected in the Hubble Space Telescope. Smith and Grunsfeld conducted the mission’s first spacewalk on Dec. 22, the flight’s fourth day in space. The duo, aided by Clervoy operating the RMS from inside Discovery, completed two of mission’s highest priority objectives. They replaced the failed gyroscopes, installing three new Rate Sensor Units, each containing two gyroscopes, to return control to the ailing telescope. They also installed six Voltage/Temperature Improvement Kits to prevent the telescope’s batteries from overheating as they aged. The excursion lasted eight hours 15 minutes, at the time the second longest spacewalk.
      During the second spacewalk, astronauts C. Michael Foale, left, and Claude Nicollier during the changeout of the fine guidance sensor. Foale at the end of the Remote Manipulator System services the Hubble Space Telescope. The next day, Nicollier and Foale conducted the mission’s second spacewalk. The main task for this excursion involved installing a new computer aboard Hubble, replacing the original 1970s vintage unit. The new radiation-hardened system ran 20 times faster and carried six times more memory while using one-third the electrical power. They also installed a fine guidance sensor before concluding the eight-hour 10-minute spacewalk.
      Astronauts Steven L. Smith, left, and John M. Grunsfeld begin their servicing activities during the third spacewalk. At the end of the third and final spacewalk, Grunsfeld, left, and Smith provide closing comments about the work the mission accomplished to service the Hubble Space Telescope. Smith and Grunsfeld ventured outside for a second time to complete the flight’s third and final spacewalk on Dec. 24, the first spacewalk conducted on Christmas Eve day. First, they replaced an old reel-to-reel tape recorder with a solid state unit providing a 10-fold increase in recording capability and replaced a failed data transmitter. They installed seven new covers on Hubble’s electronics bay doors for added protection of the telescope’s insulation. This third spacewalk lasted eight hours eight minutes.
      The first space shuttle crew to celebrate Christmas in space, the STS-103 astronauts pose wearing Santa hats. The Hubble Space Telescope shortly after the STS-103 crew released it. The next day, the STS-103 astronauts earned the distinction as the first space shuttle crew to spend Christmas Day in space. Clervoy grappled Hubble, lifted it out of the payload bay and released it to continue its mission. Hubble Space Telescope Program Manager John H. Campbell said after the release, “The spacecraft is being guided by its new gyros under the control of its brand new computer. [It] is now orbiting freely and is in fantastic shape.” After deploying Hubble, the astronauts enjoyed a well-deserved Christmas dinner, with Clervoy providing French delicacies. The crew spent Dec. 26 readying Discovery for its return to Earth, including testing its reaction control system thrusters and aerodynamic surfaces and stowing unneeded gear.
      Astronauts Steven L. Smith, left, Claude Nicollier, and John M. Grunsfeld complete their fluid loading protocol and put on their launch and entry suits prior to reentry. Space shuttle Discovery makes a perfect night landing at NASA’s Kennedy Space Center in Florida. The crew welcome home ceremony at Ellington Field in Houston. On Dec. 27, the astronauts donned their launch and entry suits and prepared for the return to Earth. They closed the payload bay doors and fired Discovery’s engines to bring them out of orbit. Just before landing, Kelly lowered the craft’s landing gear and Brown guided Discovery to a smooth night landing at KSC, concluding a flight of seven days, 23 hours, 11 minutes. They circled the Earth 119 times. The flight marked Discovery’s last solo flight as all its subsequent missions docked with the International Space Station. Workers at KSC began readying it for its next mission, STS-92 in October 2000.

      The Hubble Space Telescope continues to operate today, far exceeding the five-year life extension expected from the last of the servicing missions in 2009. Joined in space by the James Webb Space Telescope in 2021, the two instruments together continue to image the skies across a broad range of the electromagnetic spectrum to provide scientists with the tools to gain unprecedented insights into the universe and its formation.

      Watch the STS-103 crew narrate a video of their Hubble servicing mission.
      View the full article
    • By NASA
      Hubble Space Telescope Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts News Hubble News Hubble News Archive Social Media Media Resources Multimedia Multimedia Images Videos Sonifications Podcasts E-books Online Activities Lithographs Fact Sheets Glossary Posters Hubble on the NASA App More 35th Anniversary 2 min read
      Hubble Spies a Cosmic Eye
      This NASA/ESA Hubble Space Telescope image features the spiral galaxy NGC 2566. ESA/Hubble & NASA, D. Thilker This NASA/ESA Hubble Space Telescope image features the spiral galaxy NGC 2566, which sits 76 million light-years away in the constellation Puppis. A prominent bar of stars stretches across the center of this galaxy, and spiral arms emerge from each end of the bar. Because NGC 2566 appears tilted from our perspective, its disk takes on an almond shape, giving the galaxy the appearance of a cosmic eye.
      As NGC 2566 appears to gaze at us, astronomers gaze right back, using Hubble to survey the galaxy’s star clusters and star-forming regions. The Hubble data are especially valuable for studying stars that are just a few million years old; these stars are bright at the ultraviolet and visible wavelengths to which Hubble is sensitive. Using these data, researchers can measure the ages of NGC 2566’s stars, which helps piece together the timeline of the galaxy’s star formation and the exchange of gas between star-forming clouds and the stars themselves.
      Hubble regularly teams up with other astronomical observatories to examine objects like NGC 2566, including the NASA/ESA/CSA James Webb Space Telescope. Webb data complements Hubble’s by going beyond the infrared wavelengths of light Hubble can see, better defining areas of warm, glowing dust. At even longer wavelengths, the Atacama Large Millimeter/submillimeter Array (ALMA) of 66 radio telescopes that work together can capture detailed images of the clouds of gas and dust in which stars form. Together, Hubble, Webb, and ALMA provide an overview of the formation, lives, and deaths of stars in galaxies across the universe.
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      Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubble Media Contact:
      Claire Andreoli (claire.andreoli@nasa.gov)
      NASA’s Goddard Space Flight Center, Greenbelt, MD
      Share








      Details
      Last Updated Dec 19, 2024 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
      Astrophysics Astrophysics Division Galaxies Goddard Space Flight Center Hubble Space Telescope Spiral Galaxies Keep Exploring Discover More Topics From NASA
      Hubble Space Telescope


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      Hubble’s Partners in Science



      Hubble’s Night Sky Challenge



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      View the full article
    • By NASA
      This article is for students grades 5-8.
      The Sun is the star of our solar system. Its gravity holds Earth and our planetary neighbors in its orbit. At 865,000 miles (1.4 million km) in diameter, it’s the largest object in our solar system. On Earth, its influence is felt in our weather, seasons, climate, and more. Let’s learn about our dynamic star and its connections to life on Earth.
      What is the Sun, and what is it made of?
      The Sun is a yellow dwarf star. It is approximately 4.5 billion years old and is in its “main sequence” phase. This means it is partway through its lifecycle with a few billion more years ahead of it.
      The Sun is made of hydrogen and helium gases. At its core, hydrogen is fused to form helium. This nuclear reaction creates the Sun’s heat and light. That energy moves outward through the Sun’s radiative zone and convective zone. It then reaches the Sun’s visible surface and lower atmosphere, called the photosphere. Above the photosphere lies the chromosphere, which forms the Sun’s middle atmosphere, and beyond that is the corona, the Sun’s outermost atmosphere.
      The Sun is a yellow dwarf star with a complex series of layers and features.NASA What is the solar cycle?
      The Sun goes through a pattern of magnetic activity known as the solar cycle. During each cycle, the Sun experiences a very active period called “solar maximum” and a less active period called “solar minimum.”
      During solar maximum, increased magnetic activity creates sunspots. These appear as darker, cooler spots on the Sun’s surface. The more sunspots we can see, the more active the Sun is.
      The solar cycle begins at solar minimum, peaks at solar maximum, and then returns to solar minimum. This cycle is driven by the Sun’s magnetic polarity, which flips – north becomes south, and vice versa – every 11 years. It takes two cycles – or 22 years – to complete the full magnetic cycle where the poles return to their original positions.  
      The Sun’s level of magnetic activity changes throughout its 11-year solar cycle. During each cycle, the Sun experiences a less-active period called “solar minimum” (left) and a very active period called “solar maximum” (right).NASA Wait. The Sun’s magnetic poles can flip??
      Yes! Like Earth, the Sun has north and south magnetic poles. But unlike Earth, the Sun’s poles flip regularly. Each 11-year solar cycle is marked by the flipping of the Sun’s poles. The increased magnetic activity during solar maximum makes the north and south poles less defined. As the cycle moves back to solar minimum, the polarization of the poles returns – with flipped polarity.
      Unlike Earth, the Sun’s poles regularly flip with each 11-year solar cycle.NASA What is space weather?
      Space weather includes phenomena such as solar wind, solar storms, and solar flares. When space weather conditions are calm, there may be little noticeable effect on Earth. But when the Sun is more active, space weather has real impacts on Earth and in space.
      Let’s explore these phenomena and how they affect our planet.
      Periods of increased solar activity can cause noticeable effects on Earth and in space.NASA What is solar wind?
      Solar wind is a stream of charged particles that flow outward from the Sun’s corona. It extends far beyond the orbit of the planets in our solar system. When solar wind reaches Earth, its charged particles interact with Earth’s magnetic field. This causes colorful streams of moving light at Earth’s north and south poles called aurora.
      Earth’s magnetic field protects our planet from the charged solar particles of the solar wind.NASA What are solar storms, solar flares, and coronal mass ejections?
      The Sun’s magnetic fields are a tangle of constant motion. These fields twist and stretch to the point that they snap and reconnect. When this magnetic reconnection occurs, it releases a burst of energy that can cause a solar storm.
      Solar storms can include phenomena such as solar flares or coronal mass ejections. They happen more frequently around the solar maximum of the Sun’s cycle. A solar flare is an intense burst of light and energy from the Sun’s surface. Solar flares tend to happen near sunspots where the Sun’s magnetic fields are strongest. A coronal mass ejection is a massive cloud of material flowing outward from the Sun. These can occur on their own or along with solar flares.
      The Sun’s magnetic field is strongest near sunspots. These active regions of the Sun’s surface release energy in the form of solar flares and coronal mass ejections like these.NASA How do these phenomena affect Earth?
      When a solar storm erupts towards Earth, our atmosphere and magnetic field protect us from significant harm. However, some impacts are possible, both on Earth and in space. For example, strong solar storms can cause power outages and radio blackouts. GPS signals can be disrupted. Satellite electronics can be affected. And astronauts working outside of the International Space Station could be exposed to dangerous radiation. NASA monitors and forecasts space weather to protect the safety and health of astronauts and spacecraft.
      When charged particles from intense solar storms interact with Earth’s magnetic fields, colorful auroras like this one captured in Saskatchewan, Canada, can occur.NASA Learn more about the Sun
      NASA’s Parker Solar Probe launched in 2018 on the first-ever mission to fly into the Sun’s corona. Since its first pass through the corona in 2021, every orbit has brought it closer to the Sun. On Dec. 24, 2024, it makes the first of its three final, closest solar approaches of its primary mission. Test your knowledge with NASA’s new quiz, Kahoot! Parker Solar Probe trivia.
      Visit these resources for more details about the Sun:
      https://science.nasa.gov/sun/facts/ https://spaceplace.nasa.gov/all-about-the-sun/en/ https://science.nasa.gov/exoplanets/stars/ Explore More For Students Grades 5-8 View the full article
    • By USH
      The mystery of unidentified drones remains unresolved, with government authorities offering little clarity. Officials have downplayed the incidents, asserting there is no threat to national security and attributing many sightings to aircraft such as planes or helicopters. However, the lack of transparency has only fueled public speculation and heightened concerns. 

      What people/experts say: 
      Some speculate that these drones are part of covert operations designed to detect dirty bombs or nuclear devices or theses drones are part of an advanced surveillance systems operated by certain agencies. 
      The Space Force could be conducting classified exercises, such as testing cutting-edge technology or performing communication lockdown drills to evaluate detection and evasion capabilities. 
      A former CIA officer has suggested that the drones may be part of government efforts to trial advanced technologies in urban environments. 
      Reports indicate these drones exhibit unusual traits, such as lacking heat signatures and evading detection. They might employ RF jamming or encrypted communications, potentially causing unintentional disruptions to civilian electronics, including power outages, while avoiding capture. 
      Intelligence analysts have compared the drones to Russian Orlan-10 or Iranian Shahed-136 models, raising suspicions of international espionage. 
      But, the most striking statement came from Elon Musk, who warned earlier this year about the arrival of epic drone wars. He said that drone swarm battles are coming that will boggle the mind. What does he know that we don’t?
          A large drone flying at a slow speed, shooting out or launching multiple smaller drones at a relatively high speed.
         DAHBOO77 video: Musk's statement on X (formerly Twitter) at approximately the 1:23 mark.View the full article
    • By NASA
      Hubble Space Telescope Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts News Hubble News Hubble News Archive Social Media Media Resources Multimedia Multimedia Images Videos Sonifications Podcasts E-books Online Activities Lithographs Fact Sheets Glossary Posters Hubble on the NASA App More 35th Anniversary 2 min read
      Hubble Images a Grand Spiral
      This NASA/ESA Hubble Space Telescope image features the spiral galaxy NGC 5643. ESA/Hubble & NASA, A. Riess, D. Thilker, D. De Martin (ESA/Hubble), M. Zamani (ESA/Hubble) This NASA/ESA Hubble Space Telescope image features the glorious spiral galaxy NGC 5643, which is located roughly 40 million light-years away in the constellation Lupus, the Wolf. NGC 5643 is a grand design spiral, which refers to the galaxy’s symmetrical form with two large, winding spiral arms that are clearly visible. Bright-blue stars define the galaxy’s spiral arms, along with lacy reddish-brown dust clouds and pink star-forming regions.
      As fascinating as the galaxy appears at visible wavelengths, some of NGC 5643’s most interesting features are invisible to the human eye. Ultraviolet and X-ray images and spectra of NGC 5643 show that the galaxy hosts an active galactic nucleus: an especially bright galactic core powered by a feasting supermassive black hole. When a supermassive black hole ensnares gas from its surroundings, the gas collects in a disk that heats up to hundreds of thousands of degrees. The superheated gas shines brightly across the electromagnetic spectrum, but especially at X-ray wavelengths.
      NGC 5643’s active galactic nucleus isn’t the brightest source of X-rays in the galaxy, though. Researchers using ESA’s XMM-Newton discovered an even brighter X-ray-emitting object, called NGC 5643 X-1, on the galaxy’s outskirts. What could be a more powerful source of X-rays than a supermassive black hole? Surprisingly, the answer appears to be a much smaller black hole! While the exact identity of NGC 5643 X-1 is unknown, evidence points to a black hole that is about 30 times more massive than the Sun. Locked in an orbital dance with a companion star, the black hole ensnares gas from its stellar companion, creating a superheated disk that outshines the NGC 5643’s galactic core.
      NGC 5643 was also the subject of a previous Hubble image. The new image incorporates additional wavelengths of light, including the red color that is characteristic of gas heated by massive young stars.
      Explore More

      Hubble’s Galaxies


      Science Behind the Discoveries: Black Holes


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      Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubble Media Contact:
      Claire Andreoli (claire.andreoli@nasa.gov)
      NASA’s Goddard Space Flight Center, Greenbelt, MD
      Share








      Details
      Last Updated Dec 12, 2024 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
      Astrophysics Astrophysics Division Galaxies Goddard Space Flight Center Hubble Space Telescope Spiral Galaxies Keep Exploring Discover More Topics From Hubble
      Hubble Space Telescope


      Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.


      Hubble’s Night Sky Challenge



      Hubble Posters



      Hubble by the Numbers


      View the full article
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