OrbitalHub

ESA dixit:

“The motion of two million stars is traced 5 million years into the future using data from the Tycho-Gaia Astrometric Solution, one of the products of the first Gaia data release. This provides a preview of the stellar motions that will be revealed in Gaia’s future data releases, which will enable scientists to investigate the formation history of our Galaxy.

Stars move through our Galaxy, the Milky Way, although the changes in their positions on the sky are too small and slow to be appreciated with the naked eye over human timescales. These changes were first discovered in the eighteenth century by Edmond Halley, who compared stellar catalogues from his time to a catalogue compiled by the astronomer Hipparchus some two thousand years before. Nowadays, stellar motions can be detected with a few years’ worth of high-precision astrometric observations, and ESA’s Gaia satellite is currently leading the effort to pin them down at unprecedented accuracy.

A star’s velocity through space is described by the proper motion, which can be measured by monitoring the movement of a star across the sky, and the radial velocity, which quantifies the star’s motion towards or away from us. The latter can be inferred from the shift towards blue or red wavelengths of certain features – absorption lines – in the star’s spectrum.

Launched in 2013, Gaia started scientific operations in July 2014, scanning the sky repeatedly to obtain the most detailed 3D map of our Galaxy ever made. The first data release, published in September 2016, was based on data collected during Gaia’s first 14 months of observations and comprised a list of 2D positions – on the plane of the sky – for more than one billion stars, as well as distances and proper motions for a subset of more than two million stars in the combined Tycho–Gaia Astrometric Solution, or TGAS.
The TGAS dataset consists of stars in common between Gaia’s first year and the earlier Hipparcos and Tycho-2 Catalogues, both derived from ESA’s Hipparcos mission, which charted the sky more than two decades ago.

This video shows the 2 057 050 stars from the TGAS sample, with the addition of 24 320 bright stars from the Hipparcos Catalogue that are not included in Gaia’s first data release. The stars are plotted in Galactic coordinates and using a rectangular projection: in this, the plane of the Milky Way stands out as the horizontal band with greater density of stars. Brighter stars are shown as larger circles, and an indication of the true colour of each star is also provided; information about brightness and colour is based on the Tycho-2 catalogue from the Hipparcos mission.

The video starts from the positions of stars as measured by Gaia between 2014 and 2015, and shows how these positions are expected to evolve in the future, based on the proper motions from TGAS. The frames in the video are separated by 750 years, and the overall sequence covers 5 million years. The stripes visible in the early frames reflect the way Gaia scans the sky and the preliminary nature of the first data release; these artefacts are gradually washed out in the video as stars move across the sky.”

Video credit: ESA

NASA dixit:

“The Solar Dynamics Observatory (SDO) has now captured nearly seven years worth of ultra-high resolution solar footage. This time lapse shows that full run from two of SDO’s instruments. The large orange sun is visible light captured by HMI. The smaller golden sun is extreme ultraviolet light from AIA and reveals some of the suns atmosphere, the corona. Both appear at one frame every 12 hours. SDO’s nearly unbroken run is now long enough to watch the rise and fall of the current solar cycle. The graph of solar activity shows the sunspot number, a measurement based on the number of individual spots and the number of sunspot groups. In this case, the line represents a smoothed 26-day average to more clearly show the overall trend.”

Video credit: NASA’s Goddard Space Flight Center/Scott Wiessinger

Wikipedia dixit:

“The Hubble Space Telescope (HST) is a space telescope that was launched into low Earth orbit in 1990, and remains in operation. Although not the first space telescope, Hubble is one of the largest and most versatile, and is well known as both a vital research tool and a public relations boon for astronomy. The HST is named after the astronomer Edwin Hubble, and is one of NASA’s Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope.

With a 2.4-meter (7.9 ft) mirror, Hubble’s four main instruments observe in the near ultraviolet, visible, and near infrared spectra. Hubble’s orbit outside the distortion of Earth’s atmosphere allows it to take extremely high-resolution images, with substantially lower background light than ground-based telescopes. Hubble has recorded some of the most detailed visible light images ever, allowing a deep view into space and time. Many Hubble observations have led to breakthroughs in astrophysics, such as accurately determining the rate of expansion of the universe.

The HST was built by the United States space agency NASA, with contributions from the European Space Agency. The Space Telescope Science Institute (STScI) selects Hubble’s targets and processes the resulting data, while the Goddard Space Flight Center controls the spacecraft.

Space telescopes were proposed as early as 1923. Hubble was funded in the 1970s, with a proposed launch in 1983, but the project was beset by technical delays, budget problems, and the Challenger disaster (1986). When finally launched in 1990, Hubble’s main mirror was found to have been ground incorrectly, compromising the telescope’s capabilities. The optics were corrected to their intended quality by a servicing mission in 1993.

Hubble is the only telescope designed to be serviced in space by astronauts. After launch by Space Shuttle Discovery in 1990, four subsequent Space Shuttle missions repaired, upgraded, and replaced systems on the telescope, including all five of the main instruments. A fifth mission was canceled on safety grounds following the Columbia disaster (2003). However, after spirited public discussion, NASA administrator Mike Griffin approved one final servicing mission, completed in 2009. The telescope is operating as of 2016, and could last until 2030–2040. Its scientific successor, the James Webb Space Telescope (JWST), is scheduled for launch in 2018.”

Video credit: NASA Goddard

NASA dixit:

“This artist’s rendering illustrates new findings about a star shredded by a black hole. When a star wanders too close to a black hole, intense tidal forces rip the star apart. In these events, called “tidal disruptions,” some of the stellar debris is flung outward at high speed while the rest falls toward the black hole. This causes a distinct X-ray flare that can last for a few years. NASA’s Chandra X-ray Observatory, Swift Gamma-ray Burst Explorer, and ESA/NASA’s XMM-Newton collected different pieces of this astronomical puzzle in a tidal disruption event called ASASSN-14li, which was found in an optical search by the All-Sky Automated Survey for Supernovae (ASAS-SN) in November 2014. The event occurred near a super-massive black hole estimated to weigh a few million times the mass of the sun in the center of PGC 043234, a galaxy that lies about 290 million light-years away. Astronomers hope to find more events like ASASSN-14li to test theoretical models about how black holes affect their environments.

During the tidal disruption event, filaments containing much of the star’s mass fall toward the black hole. Eventually these gaseous filaments merge into a smooth, hot disk glowing brightly in X-rays. As the disk forms, its central region heats up tremendously, which drives a flow of material, called a wind, away from the disk.”

Video credit: NASA’s Goddard Space Flight Center

NASA dixit:

“The sun is always changing and NASA’s Solar Dynamics Observatory is always watching. Launched on Feb. 11, 2010, SDO keeps a 24-hour eye on the entire disk of the sun, with a prime view of the graceful dance of solar material coursing through the sun’s atmosphere, the corona. SDO’s sixth year in orbit was no exception. This video shows that entire sixth year — from Jan. 1, 2015, to Jan. 28, 2016, as one time-lapse sequence. At full quality on YouTube, this video is ultra-high definition 3840×2160 and 29.97 frames per second. Each frame represents 2 hours. […]

SDO’s Atmospheric Imaging Assembly (AIA) captures a shot of the sun every 12 seconds in 10 different wavelengths. The images shown here are based on a wavelength of 171 angstroms, which is in the extreme ultraviolet range and shows solar material at around 600,000 kelvins (about 1,079,540 degrees F). In this wavelength it is easy to see the sun’s 25-day rotation.

During the course of the video, the sun subtly increases and decreases in apparent size. This is because the distance between the SDO spacecraft and the sun varies over time. The image is, however, remarkably consistent and stable despite the fact that SDO orbits Earth at 6,876 mph, and Earth orbits the sun at 67,062 mph.

Scientists study these images to better understand the complex electromagnetic system causing the constant movement on the sun, which can ultimately have an effect closer to Earth, too. Flares and another type of solar explosion called coronal mass ejections can sometimes disrupt technology in space. Moreover, studying our closest star is one way of learning about other stars in the galaxy. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, built, operates and manages the SDO spacecraft for NASA’s Science Mission Directorate in Washington, D.C.”

Video credit: NASA’s Goddard Space Flight Center/Wiessinger

Music credit: “Tides,” a track available from Killer Tracks

NASA dixit:

“It’s always shining, always ablaze with light and energy that drive weather, biology and more. In addition to keeping life alive on Earth, the sun also sends out a constant flow of particles called the solar wind, and it occasionally erupts with giant clouds of solar material, called coronal mass ejections, or explosions of X-rays called solar flares. These events can rattle our space environment out to the very edges of our solar system. In space, NASA’s Solar Dynamics Observatory, or SDO, keeps an eye on our nearest star 24/7. SDO captures images of the sun in 10 different wavelengths, each of which helps highlight a different temperature of solar material. In this video, we experience SDO images of the sun in unprecedented detail. Presented in ultra-high definition, the video presents the dance of the ultra-hot material on our life-giving star in extraordinary detail, offering an intimate view of the grand forces of the solar system.”

Video credit: NASA Goddard