Black holes are some of the most mind-bending and intriguing objects in the universe. With some containing billions of times the mass of our Sun, black holes both let us explore the limits of our own universe and allow our imaginations to run wild. Inside the Black Holes Space & Beyond Box, you’ll find a unique collection of items hand-picked just for you by the editors of Astronomy magazine. Below is a look at just a few.

Tungsten black hole model

In 1915, Albert Einstein published his now-famous equations of general relativity. Within two months, German physicist Karl Schwarzschild had derived the simplest solution to these equations, showing that if you squeeze any object down small enough, it will become a black hole.

A key part of this solution is the Schwarzschild radius: the distance from any object where the pull of its gravity becomes so strong that even light cannot escape. In other words, the Schwarzschild radius is the point of no return. A black hole’s event horizon sits at the distance of its Schwarzschild radius.

In this month’s Space & Beyond Box, you’ll find something truly unique: A tungsten sphere exactly the size Earth would be if you compressed our planet into a black hole. But don’t be fooled by its size — pick it up, and you’ll see it’s quite heavy. That’s because tungsten, which is 74th on the periodic table, is one of the densest materials in the universe. This gives you better feel for just how dense our planet would be as a black hole.

Included are a stand for displaying your Earth-mass black hole and an informational card that shows how to calculate the Schwarzschild radius for any object — even yourself!

Kip Thorne’s Black Hole Presentation Digital Download

Along with Albert Einstein and Stephen Hawking, the name Kip S. Thorne is inextricably linked with the subject of black holes. In 1974, he and Hawking famously made a bet over whether the strange object Cygnus X-1 was indeed a black hole. Thorne, who bet that it was a black hole, won. In 2017, Thorne was one of three physicists awarded the Nobel Prize in Physics for his work leading to the detection of gravitational waves. He even served as science advisor and executive producer on the movie Interstellar.

Inside your Space & Beyond Box, you’ll receive a digital download for an excerpt from Thorne’s 2011 talk at the Starmus Festival in Tenerife, Spain. This is your exclusive opportunity to hear a pivotal figure who has shaped our understanding of modern astrophysics discuss his work on black holes, gravitational waves, and much more. If you want to know the state of our current understanding of black holes, this is your ticket.

Also included is a free downloadable guide from the 2014 Starmus festival, with detailed information about how black holes influence their environment, how they generate gravitational waves, and how researchers today use sophisticated observatories such as LIGO to detect these delicate ripples in space-time.

Black holes postcard pack

Astronomers now believe all large galaxies have supermassive black holes weighing millions to billions of times the mass of our Sun in their cores. These black holes, although invisible, can wreak beautiful havoc on their surroundings, from ruling the orbits of nearby gas, dust, and stars to shooting out jets of material far beyond their galaxy.

Included in the Black Holes Space & Beyond Box is a set of 10 stunning color postcards, each showing a famous galaxy that hides a monster black hole at its center. Every card includes a short explanation of the object. Journey from the nearby Andromeda Galaxy, shown in unprecedented detail, to the more distant NGC 4889, which houses one of the most massive black holes known. Some galaxies, like Perseus A and Cygnus A, appear tangled and twisted by their black holes’ influence. Others, such as the Sombrero Galaxy (M104), look almost placid. The elliptical galaxy M87, shown with its famous 5,000 light-year-long jet, is home to the first supermassive black hole ever imaged.

This specially curated collection is ideal for both home display and sharing through the mail with family and friends.

Black holes 500-piece jigsaw puzzle

What does a black hole look like? Find out piece by piece as you assemble the 500-piece jigsaw puzzle, “The Power of a Supermassive Black Hole,” included in your Space & Beyond Box.

This exclusive puzzle shows a sophisticated artist’s depiction of a black hole, which sits at the center of a dark sphere. The sphere itself is the event horizon — anything that crosses this boundary is destined to fall into the black hole. Swirling around it is a glowing accretion disk of heated dust, gas, and other material flowing toward the black hole like water down a drain. And blasting outward at near-light-speed is a bright jet of material, carrying away a small fraction of material from the disk into space. Such jets are among of the most powerful particle accelerators in the universe, responsible for creating high-energy cosmic rays.

Completing this puzzle will take you on a journey to the inner regions of a black hole, where you’ll get a ringside seat to some of the most amazing action in the universe.