Spacecraft discovers thousands of doomed comets
The ESA/NASA Solar and Heliospheric Observatory has discovered more than 3000 doomed comets that have passed close to the sun.
The Solar and Heliospheric Observatory, better known as "SOHO", is a joint project of the European Space Agency, or ESA, and NASA. Orbiting the sun at 1.5 million km, or 932,000 miles from Earth, the distant observatory has just discovered its 3000th comet-more than any other spacecraft or astronomer. And, just about all of SOHO's comets have been destroyed.
"They just disintegrate every time we observe one," said Karl Battams, a solar scientist at the Naval Research Labs in Washington, D.C., who has been in charge of running the SOHO comet-sighting website since 2003. "SOHO sees comets that pass very close to the sun-and they just can't stand the intense sunlight."
The overwhelming majority of SOHO's comet discoveries belong to the Kreutz family. Kreutz sungrazers are fragments from the breakup of a single giant comet thousands of years ago. They get their name from 19th century German astronomer Heinrich Kreutz, who studied them in detail. On average, a new member of the Kreutz family is discovered every three days. Unfortunately for these small comets, their orbits swoop perilously close to the sun.
There's only one Kreutz comet that made it around the sun – Comet Lovejoy. And we are pretty confident it fell apart a couple of weeks afterwards
Although SOHO's comets are rapidly destroyed, they nevertheless have great scientific value. For instance, the comets' tails are buffeted and guided by the sun's magnetic fields. Watching how the tails bend and swing can tell researchers a great deal about the sun's magnetic field.
Prior to the launch of SOHO in 1995, only a dozen or so comets had ever even been discovered from space, while some 900 had been discovered from the ground since 1761. SOHO has turned the tables on these figures, making itself the greatest comet hunter of all time.
But SOHO hasn't reached this lofty perch alone. The spacecraft relies on people who sift through its data. Anyone can help because SOHO's images are freely available online in real time. Many volunteer amateur astronomers scan the data on a daily basis for signs of a new comet. The result: 95% of SOHO comets have been found by citizen scientists.
Whenever someone spots a comet, they report it to Battams. He goes over the imagery to confirm the sighting and then submits it to the Central Bureau for Astronomical Telegrams, which gives it an official name.
And the name is…you guessed it. "SOHO."
While comets spotted from the ground are named after the person who first discovered them, comets first observed by a space-based telescope are named after the spacecraft. The 3000th comet discovered was named "SOHO-3000."
Naturally, it has already been destroyed. SOHO doesn't mind though. The Greatest Comet Hunter Ever has already moved on to the next sungrazer.
"SOHO-4000," anyone?
Big Mystery in the Perseus Cluster
A mysterious X-ray signal from the Perseus cluster of galaxies, which researchers say cannot be explained by known physics, could be a key clue to the nature of Dark Matter.
The Perseus galaxy cluster is one of the most massive objects in the universe. It contains more than 1,000 galaxies, it's located about 240 million light-years away and at its center, there's a supermassive back whole. It caught scientists' attention in 1970 when a high X-ray emission was detected during an Aerobee rocket flight. When observed in the X-ray band, the Perseus cluster is the brightest cluster in the sky.
The Perseus cluster (Abell 426) is a cluster of galaxies in the constellation Perseus. It has a recession speed of 5,366 km/s and a diameter of 863.
It is one of the most massive objects in the known universe, containing thousands of galaxies immersed in a vast cloud of multimillion-degree gas.
An innovative interpretation of X-ray data from a galaxy cluster could help scientists understand the nature of dark matter. The finding involves a new explanation for a set of results made with NASA's Chandra X-ray Observatory, ESA's XMM-Newton and Hitomi, a Japanese-led X-ray telescope. If confirmed with future observations, this may represent a major step forward in understanding the nature of the mysterious, invisible substance that makes up about 85% of matter in the universe.
The image shown here contains X-ray data from Chandra (blue) of the Perseus galaxy cluster, which has been combined with optical data from the Hubble Space Telescope (pink) and radio emission from the Very Large Array (red). In 2014, researchers detected an unusual spike of intensity, known as an emission line, at a specific wavelength of X-rays (3.5 keV) in the hot gas within the central region of the Perseus cluster. They also reported the presence of this same emission line in a study of 73 other galaxy clusters.
In the subsequent months and years, astronomers have tried to confirm the existence of this 3.5 keV line. They are eager to do so because it may give us important clues about the nature of dark matter. However, it has been debated in the astronomical community exactly what the original and follow-up observations have revealed.
A new analysis of Chandra data by a team from Oxford University, however, is providing a fresh take on this debate. The latest work shows that absorption of X-rays at an energy of 3.5 keV is detected when observing the region surrounding the supermassive black hole at the center of Perseus. This suggests that dark matter particles in the cluster are both absorbing and emitting X-rays. If the new model turns out to be correct, it could provide a path for scientists to one day identify the true nature of dark matter. For next steps, astronomers will need further observations of the Perseus cluster and others like it with current X-ray telescopes and those being planned for the next decade and beyond.
