Object 103: PSR B1509-58

Podcast release date: 24 July 2023

Right ascension: 15:13:55.5


Epoch: ICRS

Constellation: Circinus

Corresponding Earth location: An Area of the Pacific Ocean slightly less than 1600 km north of Mount Siple off the coast of Antarctica

This episode's coordinates point to a location in the constellation Circinus, another southern hemisphere constellation created by eighteenth century professional astronomer and professional weirdo Nicolas Louis de Lacaille [1]. I could spend more time mocking this constellation, but I think the best thing to do is to read the description of this constellation from Ian Ridpath's Star Tales [1]: "An insignificant constellation representing a pair of dividing compasses as used by geometers, draughtsmen, and navigators for drawing circles and measuring distances; they are also known as dividers." Naturally, the constellation doesn't look anything like this.

Anyhow, the specific object that this episode's coordinates point to is PSR B1509-58. The PSR in the name of this object stand for pulsar. The digits are the coordinates of the pulsar but in the 1950 coordinate system (and the coordinate system is typically designated with a B). This is why the digits in the object's name don't quite match up with the coordinates from the random number generator.

Anyway, PSR B1509-58 is a pulsar. A pulsar is a type of rapidly-rotating neutron star, which is the inert core of a very large star that has exploded as a supernova. These stars usually have masses about a couple times the mass of the Sun, and that mass is compressed into spheres with diameters of about 20 km. As indicated by their name, neutron stars are made mostly out of neutrons; the gravity is so strong in these objects that the eletrons and protons have been forced to merge together, which changes them into neutrons.

For reference, PSR B1509-58 has a rotational period of 150 milliseconds, or, in other words, it rotates about 6.67 times a second [2, 3]. That seems fast, but the Milky Way contains a lot of pulsars that rotate more quickly than this, so it isn't that fast. Still, I thought that was a cool statistic worth mentioning. Also, the distance to the pulsar, because everyone wants to know the distance to everything, is about 17000 light years (5.2 kpc) [4]. It's not that close but not that far either.

The first thing that I thought was really interesting about this pulsar is that, while many other pulsars have been discovered in radio surveys of the sky, PSR B1509-58 is one of the fewer pulsars that have been discovered in an X-ray survey. The object was originally identified in 1982 by people working with the Einstein Observatory, the first X-ray telescope that was capable of making astronomical images [2], but radio observations soon afterwards confirmed that the object is indeed a pulsar [3].

The second really interesting thing about PSR B1509-58 is that it is a relatively young pulsar. It is estimated to be roughly 1700 years old [5]. This almost seems like the type of supernova that could have been found by ancient astronomers somewhere, particularly in China, which had a reputation for doing really good work on supernova and comet observations before the invention of the telescope. However, none of the supernovae seen by the ancient Chinese astronomers or anyone else seem to match up with PSR B1509-58 [6]. This was a supernova explosion that simply went unseen.

The third really interesting thing about PSR B1509-58 is that it sits within the remnant of the supernova that formed it. That supernova remnant, which has the designation MSH 15-52, is basically a giant cloud of X-ray emitting gas about 150 light years wide that looks like a hand [7], although it's a hand with only three fingers and a thumb, and one of those fingers is a bit hard to see. Maybe it was a hand drawn by an AI. Anyway, the fingers are colliding with another oval-shaped cloud of gas named RCW 89, and it looks like the gas in RCW 89 is getting really heated up by the collision. The system looks so exotic that NASA has even published a picture of the X-ray emission [8].

So I think what attracts most professional astronomers to PSR B1509-58 is that it produces a lot of X-ray emission and even gamma ray emission and it sits within a supernova remnant that produces even more X-ray and gamma ray emission [9, 10, 11]. However, I think most other people, including me, will think this is cool because of the giant X-ray hand.


[1] Ridpath, Ian, Star tales, 1988

[2] Seward, F. D. and Harnden, F. R., Jr., A new, fast X-ray pulsar in the supernova remnant MSH 15-52., 1982, Astrophysical Journal Letters, 256, L45

[3] Manchester, R. N. et al., Discovery of radio pulsations from the X-ray pulsar in the supernova remnant G 320.4-1.2, 1982, Astrophysical Journal Letters, 262, L31

[4] Gaensler, B. M. et al., SNR G320.4-01.2 and PSR B1509-58: new radio observations of a complex interacting system, 1999, Monthly Notices of the Royal Astronomical Society, 305, 724

[5] Kaspi, V. M. et al., On the Spin-down of PSR B1509-58, 1994, Astrophysical Journal Letters, 422, L83

[6] Clark, David H. and Stephenson, Francis Richard, The historical supernovae, 1977

[7] DeLaney, T. et al., Time Variability in the X-Ray Nebula Powered by Pulsar B1509-58, 2006, Astrophysical Journal, 640, 929

[8] Chandra X-Ray Observatory, PSR B1509-58: A Young Pulsar Shows its Hand, 2009

[9] Gunji, S. et al., Observation of Pulsed Hard X-Rays/ gamma -Rays from PSR 1509-58, 1994, Astrophysical Journal, 428, 284

[10] Harding, Alice K. et al., Photon-Splitting Cascades in Gamma-Ray Pulsars and the Spectrum of PSR 1509-58, 1997, Astrophysical Journal, 476, 246

[11] Chen, Ge et al., NuSTAR Observations of the Young, Energetic Radio Pulsar PSR B1509-58, 2016, Astrophysical Journal, 817, 93


Podcast and Website: George J. Bendo

Music: Immersion by Sascha Ende

Sound Effects: Dalibor, Daronoxus, G_M_D_THREE, Guinamun, ivolipa, jameswrowles, mooncubedesign, shoba, von_Gardener, and Xulie at The Freesound Project

Image Viewer: Aladin Sky Atlas (developed at CDS, Strasbourg Observatory, France)