Black holes can be difficult to spot for the obvious reason that they don’t emit any light of their own. In May 2020, astronomers using a telescope at the European Southern Observatory in La Silla, Chile, announced that they had spotted the nearest known black hole to Earth. Led by the ESO’s Thomas Rivinius, the team had observed what they thought was a triple system that comprised two stars and a black hole. The system is called HR 6819 and is a little over 1100 light–years from Earth. That is so close that its two stars can be seen in the southern sky. The team thought that the system contained a black hole because that would explain the unusual motions of the two stars. They proposed that one of the stars orbits the black hole every 40 days and the other star is orbiting at a distance.
The claim was contested by some astronomers and a team led by Julia Bodensteiner, then a PhD student at KU Leuven in Belgian, came up with an alternative proposal. Instead, the two stars orbited each other in 40 days and there is no black hole. For this to be true, one of the stars would have to have been “stripped”. This involves a large amount of material being transferred from one star to the other in a process that is also called “stellar vampirism”.
The two teams joined forces under KU Leuven’s Abigail Frost to work out which configuration best described HR 6819. The used the ESO’s Very Large Telescope (VLT) and Very Large Telescope Interferometer (VLTI) to observe the system in higher resolution. They did not see a star orbiting in a wide orbit, but instead saw two stars in a tight orbit and separated by one third the distance from the Earth to the Sun. So, no black hole is needed. The research is described in Astronomy and Astrophysics.
Sprinting dinosaur
Would the Jamaican sprinter Usain Bolt be able to beat a 400 kg dinosaur in a 100 m race? It’s a question not many would have pondered, but Scott Lee, a physicist at the University of Toledo in Ohio, thought it would be a good problem for his students to solve. To make it a fair race, Lee chose the theropod dinosaur Dilophosaurus wetherilli, given it is thought to have a top running speed of about 10 m/s, which is about the same as Bolt’s average velocity when he set the 100 m sprint world record of 9.58 s at the 2009 World Championships in Berlin.
Using concepts from 1D kinematics and numerical techniques, the students discovered that Bolt’s lightning-fast (pun intended) acceleration at the start would leave the dilophosaurus in the dust as he wins the race with 2 s to spare. Given that the dilophosaurus had razor-sharp claws and the ability to spit venom at its prey (as DNA thief Dennis Nedry discovered in the hit-film Jurassic Park), if any race occurred then it would guarantee Bolt smashing his own record. The calculations are described in The Physics Teacher.
After delays and fears of cancellation, the James Webb Space Telescope (JWST) finally launched on Christmas Day 2021. The mission has taken its position in orbit around the Sun and NASA has released a very blurry first image taken by the telescope as its mirrors are aligned. If all goes well, the first proper images from the telescope should be available in June.
Oh my gods y’all: James Webb Space Tele-Soap. It smells *amazing*. Made by someone in our extended family, we just unexpectedly got a gift box in the mail, and it is totally delightful. Buy your own at https://t.co/w1DCkRw4Lr #JWST pic.twitter.com/gMPPulnoCv
— Molly Peeples (@astronomolly) March 3, 2022
While you are waiting for the first (hopefully) dazzling images, you could check out the amazing array of JWST-inspired products that are available to buy. I came across this phenomenon via a tweet from Molly Peeples (@astronomolly). It included a photo of a bar of “James Webb Tele-soap”, which is emblazoned with the JWST’s now iconic mirror plus a few stars, galaxies and planets. It is made by the Canterbury Soap Works in the US, but sadly it has sold out on the e-commerce website etsy. However, if you do a search on etsy, you will find hundreds of JWST-themed items including mugs, t-shirts and (of course) mirrors.
